The present invention relates generally to an image forming system, and more specifically to methods and apparatus for adjusting image formation used for semiconductor process.
Current integrated circuit (IC) manufacturing practices use lithography photomasks (reticles) to apply various patterns to a photosensitized semiconductor wafer used to create the ICs. Reticles are typically high-precision plates that contain a pattern of extremely small images of the various components of an electronic circuit. A reticle is used as a master to transfer a plurality of the circuit patterns onto a photosensitized wafer. Current state-of-the-art lithographic systems often must position an ultra-fine image to within 15 nanometers. Current circuit architectures often have conductor linewidths as narrow as 30 nanometers. Accordingly, lithography processing equipment requires advanced precision optical and mechanical systems and even higher precision systems will be required in the future, as still smaller images become common.
Lithographic exposure apparatuses are used to project images from the reticle onto the photosensitized wafer during semiconductor processing. A typical exposure apparatus includes a base frame having a lower enclosure that contains a wafer stage for holding a semiconductor wafer workpiece. The base frame also supports an optical device that holds a reticle stage and is arranged to project the images from a reticle carried by the reticle stage onto the wafer workpiece. The base frame typically supports the optical device through a vibration isolation system designed to damp and isolate vibrations between components of exposure apparatus so that vibrations in one component are not transmitted to the other.
In some lithography systems a reticle is moved synchronously with a wafer to allow an image formed by the reticle to be patterned onto the wafer. For various reasons, the resulting image from the reticle may not be imaged at the desired location on the wafer. The prior art may try to shift the reticle or wafer to correct this positional error. Such corrective movements of the already moving reticle or wafer may be difficult. Also, synchronization error can be a problem in conventional systems.
As such, it becomes increasingly necessary to devise a system that provides low reaction forces generated by the actuation of the optical element, thus avoiding transmission of vibration to other elements of the system.